Abundance, community structure and diversity of nitrifying bacterial enrichments from low and high saline brackishwater environments.

The study reports diversity in nitrifying microbial enrichments from low (0.5-5‰) and high (18-35‰) saline ecosystems. Microbial community profiling of AOB and NOB enrichments were analysed by sequencing 16S rRNA and were processed using Mothur pipeline. The α-diversity indices showed the richness of nitrifying bacterial consortia from the high saline environment and were clustering based on the source of the sample. AOB and NOB enrichments from both the environments showed diverse lineages of phyla distributed in both groups with 38 and 34 phyla from low saline and 53 and 40 phyla in high saline sources respectively. At class level α and ϒ-Proteobacteria were found to be more dominant in both the enrichments. AOB and NOBs in enrichments from low saline environments were dominated by Nitrosomonadaceae, Gallionellaceae (Nitrotoga spp.) and Ectothiorhodospiraeceae and Nitrospira respectively. Though Chromatiaceae were present in both AOB and NOB enrichments Nitrosoglobus and Nitrosococcus dominated the AOB while NOB was dominated by uncultured genera, while Rhizobiales were found in both the enrichments. AOB and NOBs in enrichments from high saline environments were dominated by Nitrospira-like AOBs, Nitrosomonas and Nitrosococcus genera; while AOA group included Nitrosopumilus and Nitrososphaeraea genera comprising and Nitrospirae respectively. The majority of the genera obtained in both the salinities were found to be either uncultured or unclassified groups. Results of the study suggest that the AOB and NOB consortia have unique and diverse microbes in each of the enrichments, capable of functioning in aquaculture systems practiced at different salinities (0-60ppt).